Useful sp to check the list of Windows logins/users that have access to the SQL Server. Provides the list of Windows accounts along with their permissions.
The option that can be very handy is its second parameter, which when passed as 'members' lists the members of a given Windows Group. EX:
For a DBA, this option can be useful to find the list of Windows users on the Sql Server, who have aquired sysadmin rights indirectly thro Builtin\Administrators group ( Default Windows Admin group ). For more details refer BOL as its documented.
Works on 2000/2005/2008.